The present invention relates to an apparatus and method for the production of a nonwoven fabric, such as a spunbond fabric web, from thermoplastic polymers, such as polypropylene, polyethylene, polyester, nylon, and blends thereof.
Processes of the described type are known which include the steps of melting the polymer, extruding the polymer through a spinneret to form a vertically oriented curtain of downwardly advancing filaments, and then air quenching the filaments. The advancing curtain is then passed through a suction type drawing or attenuating air slot, wherein compressed air is introduced into the slot so as to draw air into the upper open end of the slot and form a rapidly moving downward stream of air in the slot. A drawing force is thereby imparted to the filaments, and upon exiting at the bottom of the slot, the filaments are deposited on a moving conveyor belt to form a continuous web. The filaments of the web are then joined to each other at their contact points by any one of several known techniques. Apparatus and processes of this general type are further disclosed for example in U.S. Pat. Nos. 3,802,817 and 4,064,605, and published EPO Application 0 230 541.
While the known apparatus and processes are satisfactory in many respects, it is recognized that the uniformity of the denier and tensile properties of the filaments are not as consistent as is desirable, and that the uniformity and quality of the resulting fabric web is accordingly deficient for many end uses.
It is accordingly an object of the present invention to provide an apparatus and method for the production of a nonwoven fabric web composed of filaments having essentially uniform denier and tensile properties.
It is a more particular object of the present to provide an apparatus and method of the described type and wherein the freshly extruded filaments are drawn by means of a force imparted in a suction type air slot and under conditions which impart an essentially uniform draw to the filaments, and such that the filaments have an essentially uniform denier and tensile properties.